Download MOVEMENT OF EARTH’S CRUST

1
MOVEMENT OF EARTH’S CRUST
By Marvin Lowe
EARTH’S CHANGING SURFACE
THE FLOATING CRUST
1
First lets have a quick review of the rock cycle...
1
Let’s watch a short clip as an intro...
2
EARTH’S CHANGING SURFACE
WEB LINK
2
EARTH’S CHANGING SURFACE
WEB LINK
3
STRUCTURE OF THE EARTH
Earth
Layer
Layer
Radius
Solid Inner Core
1300 km
Liquid Outer Core
2250 km
Mantle
2900 km
Earth’s Crust
8 to 32 km
Activity
More
The Four Layers
The Earth is composed of
four different layers. The
crust is the layer that you
live on, and it is the most
widely studied and
understood. The mantle is
much hotter and has the
ability to flow. The outer
core and inner core
are even hotter with
pressures so great you
would be squeezed into a
ball smaller than a marble if
you were able to go to the
center of the Earth!
The Crust
The Earth's Crust is
like the skin of an apple.
It is very thin in
comparison to the other
three layers. The crust
is only about 3-5 miles
(8 kilometers) thick
under the oceans
(oceanic crust) and
about 25 miles (32
kilometers) thick under
the continents
(continental crust).
The Lithospheric Plates
The crust of the Earth is broken into many pieces
called plates. The plates "float" on the soft, semirigid asthenosphere.
10
10
Convection Currents
The middle mantle
"flows" because of
convection currents.
Convection currents
are caused by the very
hot material at the
deepest part of the
mantle rising, then
cooling and sinking
again --repeating this
cycle over and over.
Convection Currents
The next time you heat anything
like soup or water in a pan you can
watch the convection
currents move in the liquid.
When the convection currents flow
in the mantle they also move the
crust. The crust gets a free ride
with these currents, like the cork in
this illustration.
Safety Caution: Don’t get your
face too close to the boiling water!
4
STRESSES In The Earth’s Crust
Stresses cause deformation.
Deformation - breaking, tilting, and folding of rock.
Before Stress
Tension
Compression
Shearing
Activity
4
STRESSES In The Earth’s Crust
Stresses cause deformation.
Deformation - breaking, tilting, and folding of rock.
Before Stress
Tension
Compression
Shearing
Activity
There are three basic deformational forces: tensional,
compressional, and transversal.
Tension: are forces that pull crustal rocks apart.
Compression: are forces that squeeze crustal rock together.
Shearing: are forces that push crustal rock horizontally and in
different directions.
(Image courtesy of Michael Kimberly, North Carolina State Univ.)
5
THESE STRESSES CAN CAUSE:
Bending or Folding
Fracture or Faulting
What is a fault?
A Fault is a crack in the Earth’s crust.
Where do faults occur?
Most faults occur on
tectonic plate boundaries.
However there are some
faults in the middle of
plate boundaries.
6
KINDS OF FAULTS
Normal Fault
Thrust Fault
Reverse Fault
Strike Slip
8
FOLDING
Fold - A bend in rock caused by stress.
Anticline - An upward fold in rock.
Syncline - A downward fold in rock.
Folding
Activity
Q
Type of Fault
Type of
Stress
Normal
Tension
Thrust
Compression
Strike-Slip
Shearing
Image
20
Strike-Slip Faults
• A type of fault where rocks on either
side move past each other sideways
with little up-or down motion.
• Shearing causes these types of faults
Normal Faults
• A type of fault where the hanging
wall slides downward
• Tension forces cause normal faults
Reverse Faults
• A type of fault where the hanging
wall slides up
• Compression forces cause reverse
faults
9
FAULT OR FOLD
What four things determine if rock will fault or fold?
1. Temperature of the rock under pressure.
2. Amount of the stress applied.
3. Type of rock, fragile and brittle or ductile.
4. How was the stress applied, gradually and
constantly over time or suddenly.
Rapid vs. Gradual
Gradual Changes: changes that happen slowly
over time to change the surface of Earth
Rapid changes: changes that quickly change the
surface or Earth
Gradual vs. Rapid
Can you think of some gradual changes that change
the surface of Earth?
1.Rivers... they slowly carve out rock. EXAMPLE:
the grand canyon
2. Wind... sediment is slowly blown away to create
different rock features EXAMPLE: huddos, arches
Small changes over time add up to major
changes to Earth’s surface*
Gradual vs. Rapid
Can you think of some things that change
the Earth’s surface rapidly?
1. Earthquakes... in a matter of seconds
cities can have large cracks, etc.
EXAMPLE: Japan is now 10 inches
closer to the US, San Andres Fault
2. Volcanoes... eruptions change the
surface of Earth very quickly EXAMPLE:
Mt. Saint Helens eruption, lava flows in
Hawaii
Earthquakes
• Earthquakes are a result of motion within
the earth.
• This only occurs where the earth is solid
and therefore can only occur within about
8 miles of the surface
• Earthquakes provide the best evidence
regarding the interior structure of the
Earth.
Earthquakes
Earthquakes
Earthquakes
Earthquakes
• An earthquake is: A sudden
movement of the earth's crust
caused by the release of stress
accumulated along geologic
faults or by volcanic activity
• Earthquakes are
measured using seismographs
Focus is the location within the earth
Focus
where underground rock moves and
sends out earthquake waves.
Epicenter The epicenter is the
location on the surface of
the earth directly above the
focus of an earthquake
Types of WAVES...
Earthquakes produce three
types of waves...
Primary Waves (P waves)
Secondary Waves (S Waves)
Surface Waves
Seismic Travels Drawing
Wave Through of wave
Primary Solids &
Liquids
Wave
(p wave)
Secondary
Only
Wave
Solids
(s wave)
Solids
Surface
*this wave
Wave
causes the
most
damage*
Particle
Motion
Speed of
the wave
Fastest
(1st to
arrive)
slow
Combination side to
side & up and down
Slowest
(last)
38
Volcanoes...
A volcano is an opening in a planet’s
surface or crust which allows hot magma,
volcanic ash, and/or gasses to escape
from below the surface.
Volcanoes are usually found where
tectonic plates are diverging (spreading
apart)or subducting (one plate going
under the other plate).
Volcanoes...
Some volcanoes are really violent and
have large eruptions.
Some volcanoes erupt calmly.
mt. saint helens clip
Europe’s biggest volcano erupts
HAWAII
Transfer of Energy...
We have talked a little bit
through out the year about the
different ways energy is
transfered. Do you remember so
of those ways?
Transfer of Energy...
Do Earthquakes and Volcanoes
transfer energy from Earth’s
interior to the surface?
How?
Transfer of Energy...
EARTHQUAKES...
How do earthquakes transfer energy from
Earth’s interior to the surface?
Earthquakes create Seismic waves which
transfer mechanical energy
Transfer of Energy...
How do Volcanoes transfer energy from
Earth’s interior to the surface?
Volcanoes have flowing magma or hot
gasses and ash that transfer heat and
mechanical energy.
Different Forms of Energy In the
Earth
• Mechanical Energy: Energy due to motion
• Heat energy: energy due to heat
• Potential energy: energy that is built up but
not yet released
• Kinetic Energy: energy that is occurring (in
motion)
Modeling...
• Now as a table come up with a way that
you would model (show)
– erosion
– and
– the energy buildup and release in an
earthquake.
– Think of ways that you could show this in a
classroom
47
• ROCKS ROCK!!!
48
Types of WAVES...
Types of WAVES...
• Primary Waves: This is the fastest kind
of seismic wave, and, consequently,
the first to 'arrive' at a seismic station.
The P wave can move through solid
rock and fluids, like water or the liquid
layers of the earth.
Types of WAVES...
Types of WAVES...
• Secondary Waves: An S wave is slower
than a P wave and can only move through
solid rock, not through any liquid medium.
It is this property of S waves that led
seismologists to conclude that the Earth's
outer core is a liquid.
Types of WAVES...
Types of WAVES...
• Surface Waves: Travelling only through the
crust, surface waves are of a lower
frequency than body waves, and are
easily distinguished on a seismogram as a
result. Though they arrive after body
waves, it is surface waves that are almost
entirely responsible for the damage and
destruction associated with earthquakes.
This damage and the strength of the
surface waves are reduced in deeper
earthquakes.
Candy Quakes
• Materials: 1 napkin/paper towel and 1 candy bar per person (Each
group member needs to have a different type of candy bar)
• What to do:
1.Decide who is doing which type of stress
*Each person needs to do a different type of stress*
2.
3.
4.
5.
-tension -compression
-shearing
Get your materials
Take turns performing the “stress test”
Answer the questions in your bell ringer book
EAT your candy bar and clean up!
52
Candy Quakes Questions…
• 1. Fill out the following chart
Candy Bar
Stress Type Fault Type
Drawing
• 2. How is your candy bar similar to rock
layers?
53